“Elliot” confirmed it on the who is simeon hobbes? blog.
Although it’s not an official ABC game, “Elliot” says that it is a real game, not just a hoax. So the messages do present a puzzle that can still be solved, if what he/she/they say is true.
More information, as always, can be found on Lostpedia.
There is also a blog devoted to following the game, which may be the best place to keep up with what is going on. The blog has now been renamed the UNOFFICIAL Lost ARG.